C# Faktöriyel Hesaplama Kodları

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Faktöriyel
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private **** button1_Click(object sender, EventArgs e)
        {
            long sayi = 1, fakt = 1;
            sayi = long.Parse(textBox1.Text);
            for (long i = 1; i <= sayi; i++)
            {
                fakt = fakt * i;
            }
            listBox1.Items.Add(sayi+" Faktöriyel ="+fakt);
            textBox1.Clear();
        }

        private **** button2_Click(object sender, EventArgs e)
        {
            listBox1.Items.Clear();
           
        }
    }
}